The present invention relates to an apparatus for monitoring changes in density of a flowing liquid and responding thereto, as well as to a system for preventing the passage of a liquid with a density above or below a predetermined value or outside a predetermined range.
Bulk transportation of liquids is a very important factor in today's industrial scene. For example, crude oil is often transported long distances from a wellhead through a pipeline to a sea tanker, which sea tanker then transports the crude oil further to the storage tanks of a refinery. At the refinery the crude oil passes through many processes before it finally emerges as refined products. These products are then transported either in road, rail or sea tankers, or through product pipelines, to distribution depots or direct to the storage facilities of bulk users. Examples of such bulk users are power stations, factories, chemical conversion plants, transport companies and air fields. The process, as described above, is basically a continuous closed one with products having to be transported away from the refinery quickly so that more crude oil can be accepted and processed. Pumping and flow rates are often quite high. Flow rates in excess of 200 gallons per minute are usual and can often be in excess of 1,000 gallons per minute.
Materials having very different purposes, for example aviation gasoline and aviation turbine fuel, which if incorrectly identified or if cross-contaminated could result in potentially hazardous situations, often superficially resemble each other and are difficult to distinguish--most especially in closed systems at high flow rates. A further example of potentially hazardous cross-contamination is of gasoline with kerosine, paraffin, diesel fuel oil supplied in bulk to storage depots or bulk users.
The examples given above are of hydrocarbon materials, and in particular, of those hydrocarbon materials most often used as fuels. This is because with these materials there is perhaps the greatest change of cross-contamination which could produce situations which may be potentially hazardous. It will be understood, however, that there are many liquids other than hydrocarbon fuels which are transported in bulk, and where the possibility of cross-contamination or incorrect identification can exist, such a happening producing undesirable results even if not potentially hazardous.
At high flow rates, and especially in the closed type of system discussed, swift detection of off-specification material is very important since action must be taken as soon as possible to halt the flow of material or at least to divert it to a different path.
A number of apparatus exist for identification of the various liquids most often handled in bulk but most of these are highly sophisticated, comprise expensive, easily damaged parts, and need to be operated by trained operators, or they do not work sufficiently quick at the high flow rates involved.
Thus, a need exists for an apparatus for monitoring changes in density of a flowing liquid which apparatus is operable at high flow rates, is simple and robust, and which is reliable. The present invention provides such an apparatus.